This invention relates to a centering device for material conveyed on conveyor systems with pusher elements disposed on both sides of the conveyor system such that they can be moved to and fro towards the direction of the center line of the conveyor system.
Various prior art embodiments of centering devices of this type already exist. During the automatic, or largely automatic processing of workpieces such as e.g. sheet metal, timber boards, profiles or bars, the latter are usually transported up to a processing station on a conveyor system. In doing so, it is often necessary to ensure that the workpieces are more or less accurately centered in relation to the processing station. In these cases, use is made of the type of centering device in question here, i.e. anything from simple lateral guide boards to complicated constructions which are both complex and expensive.
This invention is based on the task of providing a centering device of the above kind, which, whilst being of a simple construction, also ensures a high degree of accuracy and operating reliability.
According to the invention, this task is solved with a centering device of the above-mentioned type in that the pusher elements each comprise at least two stoppers which can be moved along parallel guide components oriented towards the center line, said stoppers each being connected with one and the same endless traction element in such a way that they are driven in the same direction.
The traction element may be e.g. a toothed belt. This toothed belt is threaded to and fro around the two guide components in such a way that the two pusher elements can each be connected with two strands of the toothed belt which are moved in the same direction. Outside the working area, this toothed belt is threaded from the one guide component to the other, where it is also arranged to run to and fro in two strands. The toothed belt only requires a single drive, which moves both stoppers in the same direction.
In certain cases it may suffice to be able to push the workpiece towards the center from one side only. In other cases, however, it may be necessary to provide mirror-inverted centering devices on both opposite sides of the conveyor system.
Whilst a first embodiment of the invention with two mirror-inverted pusher elements provides for each pusher element to have its own drive, with the drives being synchronized via a common control unit, in a second embodiment of the invention the movement of the two pusher elements is provided by one and the same drive. For this purpose the two traction elements of both pusher elements can be threaded parallel to each other along a pre-defined portion and be connected here to a common slide which synchronizes the movement of the traction elements.
The drive or drives are associated with control units into which all that has to be entered is the width of the workpieces to be centered. This then allows a simple calculation of how far the stoppers have to be pushed in towards the middle.
Two stoppers disposed behind each other on the two guide components in the direction of conveyance prevent the workpieces to be centered from moving out of line. When centering flexible objects, e.g. bars, it may be necessary to provide three or more guide components with stoppers on both sides of the conveyor system.
The drive for the traction element may be a cylinder, a pneumatic cylinder for example, which is pushed forwards in line with the width of the objects into a specific position on one of the guide components from where, through its movement, it in turn moves the traction element to and fro. For this purpose the end of the piston rod of the cylinder, for example, can be rigidly connected to the corresponding guide component via one strand of the traction element. When the piston rod is extended, this strand is pulled forwards in the centering direction, with exactly the same happening to the corresponding strand on the other guide component. To adjust the starting position of the cylinder there can be a motor with a spindle, for example, which engages in a spindle nut on the cylinder housing.
This spindle nut can in turn be displaceably mounted together with the cylinder on the corresponding guide component.
The use of a simple pneumatic cylinder for the stoppers intended to push the workpieces towards the center is particularly advantageous as this is a very simple solution. The cylinder movement does not vary, so all that has to be done is move the cylinder housing into a predefined position in line with the width of the workpieces.